View Source Task Management

Task supervision tree for granted

Add :tarearbol to the list of applications and you are all set.

Infinite retries

Tarearbol.ensure fn ->
  unless Enum.random(1..100) == 42, do: raise "Incorrect answer"
  {:ok, 42}
end

# some bad-case logging
{:ok, 42}

Async execution with retries

Tarearbol.spawn_ensured({Process, :sleep, [1_000]},
  attempts: 1,
  on_success: {IO, :inspect, [[label: "Result"]]})

%Task{
  owner: #PID<0.248.0>,
  pid: #PID<0.271.0>,
  ref: #Reference<0.1612468028.2321547270.14001>
}
# <one second delay>
Result: :ok

Async execution of many tasks with retries

res = 1..20
      |> Enum.map(fn i ->
        fn -> Process.sleep(Enum.random(1..i)); i end
      end)
      |> Tarearbol.ensure_all(attempts: 1)

[{:ok, 1}, {:ok, 2}, ..., {:ok, 20}]

NB the above is synchronized against main process.

Limited amount of retries

Tarearbol.ensure fn ->
  raise "Incorrect answer"
end, attempts: 10

# some bad-case logging
{:error,
 %{job: #Function<20.87737649/0 in :erl_eval.expr/5>,
   outcome: {%RuntimeError{message: "Incorrect answer"},
    [{:erl_eval, :do_apply, 6, [file: 'erl_eval.erl', line: 668]},
     {Task.Supervised, :do_apply, 2,
      [file: 'lib/task/supervised.ex', line: 85]},
     {Task.Supervised, :reply, 5, [file: 'lib/task/supervised.ex', line: 36]},
     {:proc_lib, :init_p_do_apply, 3, [file: 'proc_lib.erl', line: 247]}]}}}

Delay between retries

Tarearbol.ensure fn ->
  unless Enum.random(1..100) == 42, do: raise "Incorrect answer"
  {:ok, 42}
end, delay: 1000

# some slow bad-case logging
{:ok, 42}

Callbacks

Tarearbol.ensure fn ->
  unless Enum.random(1..100) == 42, do: raise "Incorrect answer"
  {:ok, 42}
end, on_success: fn data -> IO.inspect(data, label: "★") end,
     on_retry: {IO, :inspect, [[label: "☆"]]} end

# some slow bad-case logging
# ⇓⇓⇓⇓ one or more of ⇓⇓⇓⇓
☆: %{cause: :on_raise,
  data: {%RuntimeError{message: "Incorrect answer"},
   [{:erl_eval, :do_apply, 6, [file: 'erl_eval.erl', line: 670]},
    {:erl_eval, :exprs, 5, [file: 'erl_eval.erl', line: 122]},
    {Task.Supervised, :do_apply, 2, [file: 'lib/task/supervised.ex', line: 85]},
    {Task.Supervised, :reply, 5, [file: 'lib/task/supervised.ex', line: 36]},
    {:proc_lib, :init_p_do_apply, 3, [file: 'proc_lib.erl', line: 247]}]}}
# ⇑⇑⇑⇑ one or more of ⇑⇑⇑⇑
★: 42
{:ok, 42}

Allowed options

• attempts integer, an amount of attempts before giving up, 0 for forever; default: :infinity
• delay the delay between attempts, default: :none; - raise: when true, will raise after all attempts were unsuccessful, or return {:error, outcome} tuple otherwise, default: false;
• accept_not_ok: when true, any result save for {:error, _} will be accepted as correct, otherwise only {:ok, _} is treated as correct, default: true;
• on_success: callback when the task returned a result, default: nil;
• on_retry: callback when the task failed and scheduled for retry, default: :debug;
• on_fail: callback when the task completely failed, default: :warn.

for :attempts and :delay keys one might specify the following values:

• integer → amount to be used as is (milliseconds for delay, number for attempts);
• float → amount of thousands, rounded (seconds for delay, thousands for attempts);
• :none → 0;
• :tiny → 10;
• :medium → 100;
• :infinity → -1, :attempts only.

Task spawning

Tarearbol.run_in fn -> IO.puts(42) end, 1_000 # 1 sec
Tarearbol.spawn fn -> IO.puts(42) end # immediately

Task draining

Tarearbol.run_in fn -> IO.inspect(42) end, 1_000 # 1 sec
Tarearbol.run_in fn -> IO.inspect(:foo) end, 1_000 # 1 sec
Tarearbol.drain
42       # immediately, from `IO.inspect`
:foo     # immediately, from `IO.inspect`
[ok: 42, ok: :foo] # immediately, the returned value(s)